Two things:
1-some gascolators provide the required filtering for the Airflow fuel pump. In my case, the Andair gascolator did the trick. Installing it between the fuel selector and the Airflow pump eliminates the need for a separate fuel filter.
Airflow specifies the required filter requirements.
2-Canadian requirements require a gascolator for all types of fuel systems (carbed, FI) at the low point of the fuel system.
Interpretation: To understand what this means, and why the requirement exists, you have to think like a water molecule. Many people install the gascolator at the low point of the fuel system and think that means that for a tail dragger, it needs to be in the wing root in order to compensate for the tail low attitude on the ground.
Water that forms (precipitates) or collects in the fuel tanks due to fuel cap leakage will stay in the tanks and may be detected by sumping the fuel drains. It will not be apparent in the gascolator unless the engine has been run with water in the tanks.
The real purpose of the gascolator is to collect (small) amounts of water contained in the fuel while the engine is running. This means that the gascolator needs to be at the low point of the fuel system in flight attitude. The design of the gascolator allows the water to collect at the bottom of the bowl and for uncontaminated fuel to flow through. This is more important for carbureted engines since water will fill the carburetor bowl and the engine will quit. For FI engines, small quantities of water pass through into the cylinders and is blown out the exhaust. This is why FI systems (in the USA) don't require a gascolator, but since it doubles as the required fuel filter when installed upstream of the fuel pump, why not use one?
It's fine to have the gascolator in the wing root, but as long as it's the low point in flight attitude, it can be in the stock Van's location or somewhere else. After the gascolator, try to keep the fuel lines running smoothly "uphill" to the engine driven fuel pump.
Once water is apparent in the gascolator, it's advisable to flush a sufficient quantity of fuel through the gascolator drain to ensure the upstream fuel lines have no residual water due to the unavoidable low points caused by the fuel line routing from tanks and fuel selector to the gascolator. This is harder to perform with a FI system because the pump is downstream of the gascolator. For carbed systems, the pump is usually upstream, so turning on the pump will help flush the system. With a FI system, extensive ground running and a re-check of the gascolator is in order.
All the words above can be summarized as:
"The gascolator is used to trap water in the fuel system while the engine is running. Subsequent discovery of water in the gascolator requires further investigation and corrective action".
Cheers
